first off we're looking at a massive website under constant updation. It may be because the contractors have stuck with a company that is bound to old techniques.

Also you should take into account that turning tables into tableless efficiently takes time and that may be an issue with high traffic websites. I agree that people should turn to theese new methods but then again there are a lot of variables to take into account including costs. Do consider that there are websites out there with massive structures. Just moving content form one medium to another would be time-consuming even for a pro crew.

I'm not taking their side nor am I blaming them for failing to upgrade, but looking at it form a branding point of view (a lot said) you just can't change your layout and technology each day something new comes off the shelf. Take AJAX for an example. I agree life would be a lot more fun if more sites used it wisely but you come to think, from a client's point of view, if it is really feasable.

In time I'm sure we'll see more and more websites turn to CSS and Web Standards.

It may be because the contractors have stuck with a company that is bound to old techniques.

Going along in line with this my 5 second guess is that they're probably bound into a CMS system of some sort. As an example take HBO. Look at it from the point of view of just their original programming: each show gets an integrated minisite, ties into the store, has forums, and has to tie into a global scheduling system that accounts for timezones and there being a bunch of different HBO variant channels as well (not to mention then also storing description/stats/etc. about each program that's being shown). The process of getting that sort of a system up and running would be a total nightmare for most development teams. So it really only stands to reason that saying "ooh, now we have to rewrite how it renders all that information" would be incredibly expensive from a business perspective.

Adding to that whole "expense of change" argument: How much business have any of those channels lost by virtue of NOT moving to XHTML/CSS? None. When there starts to be an issue with them losing market share because of it then I'm sure they'll all run furiously to catch up with the bandwagon.